1. Technical Field
The present invention relates to a method for transmitting/receiving a signal for use in a mobile communication system, and more particularly to a method for generating/transmitting a sequence based on a time-frequency domain transmission unit.
2. Background Art
The present invention relates to a method for modulating a predetermined transmission sequence in time and frequency directions at intervals of a transmission unit, generating a symbol acquired by the modulation of the predetermined transmission sequence, and transmitting the symbol at intervals of a transmission unit.
In a Universal Mobile Telecommunications System (UMTS) communication system based on the 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) scheme, a transmission end defines a Transmission Time Interval (TTI) used as a time unit capable of simultaneously transmitting at least one transmission block (i.e., upper layer transmission information). In the case of small-sized packet data such as VoIP, a slot contained in a single TTI (i.e., 1 TTI) is defined as a unit for simultaneously transmitting corresponding information. A plurality of OFDM symbols may be contained in the above-mentioned TTI in a time direction, the 3GPP LTE assumes that 14 OFDM symbols are contained in the 1 TTI and two slots are contained in the 1 TTI. This TTI definition is changed according to system categories. The present invention aims to define a format for transmitting a packet or control signal when a predetermined transmission unit is defined in a general wireless communication system.
In the meantime, the transmission unit may be adjusted in OFDM-length units on a time axis. In the case of establishing a transmission unit reference, a coverage and energy efficiency are considered. For example, a Single-Carrier Frequency Division Multiplexing (SC-FDM) scheme used as an uplink transmission scheme associated with a control signal for use in the 3GPP LTE scheme will hereinafter be described.
The most important duty of a User Equipment (UE) or terminal transferring a control signal to a Node-B is the coverage. In other words, although a bandwidth of a transmission (Tx) signal of the user equipment (UE) is not relatively large, the power must be concentrated on a single place and be transmitted to this place, and it is preferable that a variable width (PAPR) of the transmission signal may be narrow. For these purposes, the 3GPP LTE has prescribed that the SC-FDM scheme is basically used as an uplink signal transmission scheme.
FIG. 1 is a block diagram illustrating a transmission end of a conventional communication system based on the SC-FDM scheme.
The SC-FDM scheme is a transmission scheme for improving PAPR characteristics by reducing the amount of change in a signal. In the case of using the same power amplifier, a wider coverage can be implemented. As can be seen from the transmission end based on the SC-FDM scheme of FIG. 1, the most important characteristic of the SC-FDM scheme is that a transmission (Tx) signal is firstly spread out by a DFT module 101 according to the DFT scheme. This spread signal is mapped to the transmission (Tx) signal based on the OFDM symbol unit by an IFFT module 102 serving as an IDFT module.
Therefore, the transmission (Tx) signal is concentrated on a transmission frequency band, and is then transmitted to a destination. The resultant signal has the same effect as in the case in which the transmission (Tx) signal is transmitted via a single-carrier.
In the meantime, the transmission signal proposed by the 3GPP LTE scheme employing the SC-FDM scheme basically transmits information using a single OFDM symbol unit.
However, a transmission unit capable of actually transmitting a predetermined amount of information at once is a TTI or slot, so that it is preferable that the transmission (Tx) signal is constructed on the basis of the TTI or slot. A control signal proposed by the 3GPP LTE does not clearly provide a method for supporting a multi-format or acquiring various spreading gains, or a method for increasing the number of user equipments (UEs).
Specifically, in the case where the same user transmits different amounts of control signals, a control channel structure capable of easily supporting the above-mentioned control signals is required. However, no solution capable of implementing the control channel structure has been proposed.
The present invention provides an improved channel structure for transmitting a control signal. This improved channel structure can be applied to uplink/downlink channels based on a predetermined communication scheme capable of transmitting a signal via a predetermined sequence, and has no problem in a multi-cell deployment.
The present invention provides a method for guaranteeing a maximum number of sequences which can be applied to a corresponding channel via a channel structure, and transmitting/receiving a signal using the guaranteed sequences.
For these purposes, in the case of designing a control signal for use in a predetermined communication system, the present invention must consider a method for generating/transmitting a control signal using a user equipment (UE).
Provided that neighboring cells use the same sequence or the same uplink resources in a multi-cell environment, an unexpected collision may occur between the neighboring cells.
In order to discriminate between the neighboring cells, the neighboring cells may use different resources according to a predetermined rule prescribed between them. However, this method may have difficulty in a cell planning of an actual system deployment stage.
In the meantime, for example, the above-mentioned communication system may consider a method for implementing a randomization effect according to a frequency hopping- or sequence hopping-scheme. In this case, the above-mentioned randomization effect method accommodates interference between different cells without any change, so that it is disadvantageous to the system.
Therefore, the best solution for solving the above-mentioned problems is to differently use different user equipments (UEs) according to the CDM scheme using different orthogonal sequences or other sequences similar to the orthogonal sequences.
The above-mentioned solution has no need to perform the cell planning, and allows different systems to share the same resources with minimum costs. A proper number of spread sequences are required for the above-mentioned solution. However, in fact, the conventional art does not provide a method for employing a sufficient number of sequences without deteriorating a sequence performance.